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Influence of Soil Temperature and Moisture on Survival and Growth of Strands of Phymatotrichum omnivorum. J. E. Wheeler, Graduate Associate, Department of Plant Pathology, University of Arizona, Tucson 85721, Present address of senior author: Lehrstuhl für Pflanzenphysiologie, Ruhr Universität, 463 Bochum, Deutschland; R. B. Hine, Professor, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 62:828-832. Accepted for publication 25 January 1972. DOI: 10.1094/Phyto-62-828.

Strands of Phymatotrichum omnivorum on roots of cotton plants killed by the fungus during the summers of 1968 and 1969 were not viable after midsummer of 1969 and 1970, respectively. Strands buried 25 cm deep in the rhizosphere of cotton plants growing in the field did not survive longer than 3 months. Strands introduced into nonsterile Gila silt loam (GSL) at 10 C at initial moisture levels of 12, 22, and 30% (equivalent to 15, one-third, and one-tenth atmospheres tension, respectively) were viable after 9 months when moisture levels had decreased to as low as 8% (oven-dry basis). No strands survived 6 months at 27 and 32 C at the three moisture levels. Optimum strand formation occurred at 27 and 32 C in nonsterile GSL at 22 and 30% moisture levels. Strand formation was sparse at 16 and 35 C. No structures occurred at 10 or 40 C. Strands placed in nonsterile GSL at 22% moisture, germinated at 10 to 32 C, but not at 35 C.

Additional keywords: cotton.